The present invention relates to a voltage transmission circuit, a voltage transmitting circuit, and a voltage receiving circuit. Particularly, it can be preferably utilized for a voltage transmission circuit which uses an element with a relatively low withstand voltage to transmit voltages of positive and negative polarities.
Various systems arranged so that ICs (Integrated Circuits) or LSIs (large Scale Integrated circuits) share a common reference voltage have been proposed and put to practical use. In such a system adopted for e.g. a liquid crystal display (LCD: Liquid Crystal Display) or an organic EL (Electro-Luminescence) display with display panels' upsizing and the progress toward higher definition, the display driver is composed of ICs, and display driving is performed for each region of a display panel to be connected thereto. The display panel includes scan lines (gate lines), data lines (source lines) orthogonal thereto, and pixel cells each disposed at a point where the scan and data lines intersect each other. Through data lines (source lines), the display driver applies voltages, corresponding to a brightness to display at, to pixel cells connected to a line selected by the scan line (gate line) (or injects corresponding charges into the pixel cells). In a display panel having a number of pixels increased in a line direction or an upsized screen, a display driver is composed of ICs, which are connected to the data lines (source lines) in units of a number of data lines (source lines) and controlled to perform the display driving in parallel. In this case, pixels allocated to one line are driven by different display driver ICs and therefore, the continuity of displayed brightness becomes significant. The continuity of brightness is maintained by making arrangement so that display driver ICs share a common reference voltage (gradation reference voltage).
The Japanese Unexamined Patent Application Publication No. JP-A-2010-26138 discloses a technique for preventing the worsening of the quality of display by a liquid crystal display which drives a display region while operating drive circuit parts (display drivers) in cooperation. According to the technique, one drive circuit part produces a gradation reference voltage, based on which the other drive circuit parts produce gradation reference voltages. Incidentally, the gradation reference voltage described herein refers to a voltage for producing output voltages to be output from the drive circuit parts to the display panel, which is used as reference when producing gradation voltages. The output voltages of the drive circuit parts are produced from the same gradation reference voltage and therefore, the variation thereof can be suppressed.
The International Publication No. WO 01/057839 discloses a technique for preventing the worsening of the display quality by suppressing, in a display having a display driver of a master mode and a display driver of a slave mode, the drop in source voltage between the display drivers of master and slave modes. In WO 01/057839, gradation voltages are supplied from the display driver of the master mode to the display driver of the slave mode. The reduction in output impedance and the rise in input impedance are enabled by providing voltage follower circuits on transmission and reception sides respectively. Therefore, the gradation voltages suffer from almost no voltage drop in their transmission routes. As a result, in an image screen of a display, the display quality can be prevented from being worsened by deterring the deviation in bias and block unevenness (see p. 14 of WO 01/057839).